Plunger lift systems are artificial lift systems for oil and gas wells that are used during the producing life of the well when the bottom hole pressure and the gas to liquid ratio will no longer support natural flow. A plunger lift system includes a tubing string in the well casing with a well valve and lubricator at the top and a spring assembly at the bottom, and a plunger in the tubing string. The well is intermitted by shutting in the well for a selected time period to allow pressure build up and then opening the well valve for a selected period of time, allowing fluid to flow into the sales line. The plunger moves up the tubing string during the time the well valve is open and prevents liquid fall back. When the well valve is closed the plunger falls back to the bottom of the tubing string. The open and closed times for the well valve are usually controlled by a programmable controller.
Plungers are designed to seal against the interior of the tubing string during the ascent from the bottom of the well to maximize the liquid produced during the well valve open period. The plunger seal inhibits the rate of descent of the plunger back to the bottom of the well. Prior known devices, such as the plunger disclosed in U.S. Pat. No. 5,253,713 to Gregg et al., have a rod extending from the top of the plunger that opens a bypass valve that allows fluid flow through the hollow interior of a plunger. The bypass valve allows faster descent of the plunger. The rod in these prior known devices opens the valve when the rising plunger pushes with the rod against a bumper pad in the top of the lubricator. In this type of device, if the well valve is closed before the plunger reaches the top, the bypass valve does not open and the plunger descends slowly. If the controller opens the well valve before the plunger reaches the bottom of the well and the plunger surfaces without liquid on top of the plunger, the plunger could be damaged, the lubricator could be damaged and the entire wellhead could be blown off.
U.S. Pat. No. 5,427,504 to Dinning et al. discloses a plunger bypass valve with a ball shaped closure member and a spring loaded rod activator that pushes the ball into a valve seat to close the valve. This device opens the valve after the plunger reaches the lubricator at the top of the well and the pressures above and below the plunger are equalized.